Concrete blocks, also referred to as concrete masonry units (CMU's), are typically manufactured by forming them into various shapes as part of an automated process employing an automated concrete block machine, such as those machines manufactured by Besser Company (Alpena, Mich.) and Columbia Machine, Inc. (Vancouver, Wash.), for example. Such machines typically employ a mold frame assembled so as to form a mold box, within which a mold cavity having a negative of a desired block shape is formed. To form a block, a pallet is moved by a conveyor system onto a pallet table, which is then moved upward until the pallet contacts and forms a bottom of the mold cavity.
A hopper is used to fill a feedbox assembly with a dry-cast concrete mixture. The feedbox assembly is then moved from a refracted or withdrawn position to an extended position over the mold frame and fills the mold cavity with concrete via the open top. A head shoe assembly is then moved into (descends) the top of the mold cavity and compresses the concrete (typically via hydraulic or mechanical means) to a desired psi rating (pounds-per-square-inch) while simultaneously vibrating the mold cavity along with the vibrating table.
As a result of the compression and vibration, the concrete reaches a level of “hardness” which enables the resulting finished block to be immediately removed from the mold cavity. To remove the finished block, the mold frame and mold cavity remain stationary while the shoe assembly, pallet, and pallet table move downward and force the finished block from the mold cavity. The conveyor system then moves the pallet bearing the finished block away and a clean pallet takes its place. This process is repeated for each block.
Feedbox assemblies typically employ agitator grids to assist in mixing and dispersing the dry cast concrete material in the feedbox so that it is evenly distributed into the mold cavity. Conventional agitator grids typically comprise a set of parallel bars that are joined by one or more cross-members, with prongs or fingers extending vertically downward form the parallel bars and into the concrete material in the feedbox. The agitator grid is then moved or vibrated so that the prongs or fingers agitate the dry cast concrete so as to better disperse the dry cast concrete material over and into the mold cavity.
In order to prevent dry cast concrete from being ejected from the feedbox and onto other parts of the concrete block machine and mold assembly while agitated, deflector or containment plates are sometimes attached to the top of the feedbox drawer. However, due to gaps between the plates, such plates blocking or deflector plates are not always effective at preventing concrete from being ejected from the feedbox during agitation.